The present invention relates to a scroll type compressor including a check valve disposed in a discharge port for communicating a scroll type compression mechanism with a discharge chamber.
Recently, in an air-conditioning system (refrigerating cycle), a scroll type compressor is adopted since it can perform compression efficiently.
As shown in FIGS. 8 and 9, the scroll type compressor comprises a scroll type compressor unit h (compression mechanism) having a combination of a stationary scroll d including an end plate a, a spiral wrap b and a peripheral wall c disposed to surround the spiral wrap b and a revolving scroll g including an end plate e and a spiral wrap f disposed upright on the end plate e.
More particularly, the compressor unit h is configured to form an airtight space i for performing a compression process between the wraps b and f by combining both the scrolls d and g so that the wraps b and f are shifted with respect to each other by a predetermined angle and are engaged with each other.
The revolving scroll g is revolved by means of a rotating shaft m having an eccentric pin k formed at an end thereof, for example, so that the airtight space i is varied by the revolution.
That is, when the revolving scroll g is revolved around an axis of the stationary scroll d by means of the rotating shaft m, a capacity of the airtight space i is reduced gradually toward the central portion from the peripheral portion of the compressor unit h, so that variation of the capacity of the airtight space i is utilized to compress gas. Although not shown, the revolving scroll g is provided with a rotation checking mechanism such as an Oldham's coupling for checking rotation of the revolving scroll g on its axis.
The scroll type compressor usually utilizes a chamber to reduce surging of discharge gas and the gas is then discharged to the outside.
More particularly, as shown in FIG. 8, formed above the compressor unit h is a discharge chamber x constituted by members such as an airtight housing v and a discharge cover w. The discharge chamber x communicates with the compressor unit h through a discharge port n. Further, the discharge chamber x also communicates with a discharge pipe y mounted to the airtight housing v.
The discharge gas compressed by the compressor unit h is introduced into the discharge chamber x in which surging of the discharge gas is reduced, and then the gas is discharged from the discharge pipe y to the outside of the compressor.
The compressor unit h is provided with a check valve o disposed in the discharge port n in order to prevent backflow of the discharge gas.
A so-called free-type check valve is used as the check valve o since its structure is very simple.
More particularly, the free-type check valve o includes a valve chest p formed on the way of the discharge port n, a valve seat q formed on a peripheral edge of an opening of a discharge port n.sub.1 in the valve chest p, a retainer r formed in a wall surface opposite to the opening the discharge port n.sub.1, and a valve element s disposed between the valve seat q and the retainer r movably.
The discharge port n.sub.1 positioned upstream of the check valve o divided by the valve chest p extends from the valve seat q to the compressor unit h and discharge ports n.sub.2 positioned downstream extend from peripheral sides of the valve chest p to the discharge chamber x.
Accordingly, when the compressor unit h is operated, the valve element s of the check valve o is displaced to the side of the retainer r in response to pressure of the discharge gas to abut against the retainer, so that the discharge port n is opened.
When the operation of the compressor unit h is stopped, pressure in the compressor unit h is reduced and accordingly the valve element s of the check valve o is moved to the side of the valve seat q to abut against the surface of the valve seat, so that the discharge port n is closed. The operation of the check valve o suppresses the backflow of the discharge gas from the discharge chamber x to the compressor unit h when the operation of the compressor is stopped, so that reverse rotation of the compressor due to the backflow is prevented.
The valve element s is attached to the retainer by means of adhesive force of oil contained in the compressor during operation of the compressor. Accordingly, even when the compressor is stopped, the valve element s is not separated from the retainer easily due to adhesive force of oil between the valve element s and the retainer r depending on the operation conditions of the compressor, so that there is a possibility that the valve element s closes the discharge port late, that is, delayed closing occurs. When the delayed closing occurs, the discharge gas flows back to the compressor unit h through the discharge port n until the valve element closes the discharge port, so that the compressor unit h is disadvantageously caused to be reversely rotated while generating large sound.